EVERYBODY knows the antioxidant vitamins contained in fruit and vegetables are good for us but should we go one step further and second guess mother nature by taking vitamin supplements too? Many of us already do.
Some take 1,000 mg tablets of vitamin C in the belief (so far unproven) that they prevent colds. Others pop vitamin E capsules with their morning muesli because they've read somewhere that vitamin E supposedly prevents heart attacks. Still others can't be bothered eating a balanced diet with adequate amounts of fruit and vegetables and so take vitamins as a kind of insurance policy. We're not always sure they'll do us good, but we are sure that they won't do us any harm either.
It's time to think again. There are hopeful signs that antioxidants may prevent heart disease and cancer, but there is a dark side to the theory. The latest evidence is that extra doses of antioxidants such as betacarotene may actually do some people a lot of harm, promoting cancer and heart disease rather than preventing them.
Most sinister of all, one large US study which was set up to test the hypothesis that betacarotene and vitamin A prevent cardiovascular disease and cancer, actually had to be stopped in its tracks when many more people in the betacarotene/vitamin A group compared to the placebo group started to die of heart attacks and cancer.
Dr David Thurnham, Professor of Nutrition at the University of Ulster and an expert in antioxidants, challenges the conventional wisdom that vitamin supplements do no harm. He believes that the vast majority of us can get the vitamins and minerals we need from a balanced and varied diet and that by trying to second guess nature we may be playing a dangerous game.
By taking supplements, you could as easily free doing yourself harm as good. There probably are optimal levels of antioxidant vitamins in the body, but what levels we do not know. We can't assume these optimal levels to be a massive amount in excess of what is normally present bin the body. The body may actually have got it right.
The amount of vitamin C contained in one orange is nature's dose. By taking 20 times more in the form of a 1,000 mg supplement, you could he actually overdosing to your detriment. Until recently, however, that hasn't been the impression given to consumers.
Books such as Martin Felt's Eat Yourself Fit With The Felt Formula claim that "using supplements to your diet can counteract the problems of modern life". Media advertising for vitamin supplements often seems to imply that they will improve your health and help you deal with stress. Such health messages contradict the mainstream medical view that we do not need to take vitamin supplements in order to be healthy if we are eating a balanced and varied diet rich in fruit and vegetables at least five generous servings each day. But vitamin supplements may be required by people with extremely poor diets. For example, several studies have revealed that single parent mothers and elderly people are especially likely to be poorly nourished. There is also a proven need for folic supplemental ion in women before conception and during the early weeks of pregnancy.
Counteracting nutritional deficiency is one thing, but can vitamin megadoses actually prevent disease in otherwise healthy, well nourished people?
The focus of research has been on the antioxidant vitamins A (betacarotene), E and C. Some of these antioxidants travel through the blood stream, others lie within the body's tissues, essentially mopping up free radicals, dangerous substances produced by the body in the process of metabolising food and producing energy.
Free radicals are formed all the time simply as a result of the fact that we live in, and breathe, an atmosphere of oxygen. Life-giving though it is, oxygen is potentially very toxic to tissues - not directly, but because it permits the formation of highly reactive compounds that have the capability of damaging DNA and thus of triggering the process that leads to abnormal cell growth and cancer.
Our bodies have evolved ways of defending themselves against free radicals. There are special enzymes naturally contained within cells in all human tissue - known as superoxide dismutase - which maintain a constant search and destroy mission.
What we don't know is whether we can increase this activity by taking extra amounts of antioxidants. It may seem "logical" that the more antioxidants you have, the more free radicals you destroy, but what happens when you take more antioxidants than you need so that there are antioxidants wandering around the body without free radicals to react with? Nobody knows yet, but the suggestion is that an overabundance of antioxidants is actually dangerous.
We already know that you can overdose on a fat-soluble vitamin like vitamin A by, say, eating too much liver. Such overdosing has been proven to cause birth defects during pregnancy.
Vitamin C has had a more benign reputation. The popular view is that you cannot harm yourself with too much vitamin C since it is water soluble and the amount you don't need is immediately washed out of the body through the urine. A clue to vitamin C's darker possibilities is a rare condition - most common in Meditteranean and tropical countries - which makes some people so sensitive to vitamin C that a supplement can rupture their red cells.
As for the normal population, new research is polarising doctors into opposing camps on the safety of excess vitamin C. Firmly in the anti-supplements camp is Professor Thurnham, who fears that people who take extra vitamin C and other antioxidants may be hastening heart disease and cancer. He explains that in people who are sick with, for example, lung cancer, vitamin C levels are low. White cells actually patrol the body scavenging vitamin C. There are two possible explanations as to why, one is that the white cells need the vitamin C for some healing process. The other more sinister possibility is that the white cells are protecting the body from an excess of vitamin C which is threatening the healing process.
But at the moment, we just don't know. And until we do, healthy people who take vitamin supplements casually without the advice of their doctor are taking a chance. The best advice may be: don't take the pill, eat the food. Food may, in fact, be your best preventive medicine. An orange, after all, is perfectly packaged and in the correct therapeutic dose.
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